26. Nearly 10000 high school students across 10 countries were surveyed about their sleep habits and their performance in school. Based on the results, the researchers concluded that lack of sleep is linked to poor grades in school. Which of the following statements regarding this study and its conclusions is truc? (a) This is an experiment. Therefore, researchers can conclude that lack of sleep causes poor grades. (b) This is an experiment. Therefore, researchers cannot conclude that lack of sleep causes poor grades (0) This is an observational study. Therefore, researchers can conclude that lack of sleep causes poor grades. (d) This is an observational study. Therefore, researchers cannot conclude that lack of sleep causes poor grades. (c) This is neither an experiment nor an observational study. 27. In a study of the effects of occupation on the lung capacity of workers, a researcher measured and compared the lung capacity 300 coal miners and 300 farm workers. Other factors that might affect lung capacity are smoking habits and exercise habits. The smoking habits of the two worker types are very similar, but the coal miners gener- ally exercise less than the farm workers. Based on this study, which of the following starements (labelled I, II and III) is/are true? I) Occupation is the response variablef II) Lung capacity is the explanatory variable. III) Exercise is a potential confounding variable. (a) Only statement I is truc (b) Only statement II is true (c ) Only statement III is true (d) More than one of these three statements is truc. (c) None of these three statements is truc. 1228. Which of the following correlation values indicates the strongest linear relationship between two quantitative variables? (a) 0.61 (b) -0.85 (c) -0.45 (d) -0.3 (@) 0.09 29. An industrial process produces items of which 90% conform to quality specifications. An inspector will take a random sample of 300 items. In the sample, the probability that r or more items will conform to quality specifications is 0.35. Using a suitable approximation that we have discussed in lectures, calculate the value of r. Choose the closest valuc. n = 30 0 (a) 268 P =. 90 (b) 276 X = 0. 35 (c) 272 (d) 108 (c) 94 30. Which of the following is a valid way of choosing a simple random sample of 8 individ- uals from a group of 80 who are attending a seminar? (a) Choose the first cight people who show up. (b) Alphabetize all attendees by last name, and choose every 10th name on the list. (c) Ask for eight volunteers. X (d) Seperate the attendees by gender and then randomly choose 4 men and 4 women. * (c) None of the methods given here will obtain a simple random sample. 13CAS fx-300ES PL 31. We would like to test the hypothesis that a = 16 versus the alternative that u # 16. You may assume that all the necessary conditions for the t-test are satisfied by the data. From an observed sample of 22 observations we calculate the t-test statistic to be t = 1.721. The p-value would be t = 1721 (a) 21 Ho : U = 16 (b) 0.05 Ha: " # 16 (c) 0.2 (ED) 0.1 1 - (c) 0.9 32. A numerical value used as a summary measure for a sample, such as sample mean, is known as a (a) population parameter statistic (c) sample parameter (d) population mean (c) None of the above answers is correct. 33. The capacity of an office building elevator is 640 kg. (i.c. not safe if the total weight exceeds 640kg) Assume that the weights of the office workers are Normally distributed with mean cqual to 75 and standard deviation cqual to 9 kg. What is the probability that the total weight of 8 randomly selected office workers exceeds the capacity of an elevator? 0.001 n = 8 672 144 (b) 0.291 600 sped mem = 25 0.058 SP = 9 (d) 0.709 () 0.942 6.241 672 640 50 0 14